The Pointy End of the Rocket

There’s a running joke around NASA that the mostimportant thing about rocket travel is that “the pointy end goes up.” Thatseems simple enough—and that’s what we expect Ares I-X to do today. But haveyou ever wondered what is ON the pointy end of the rocket? You might be surprised.

Rather than an actual point or smooth, aerodynamic surface, the very top of theAres I-X rocket is capped by an instrument called the “five-hole probe.” As itsname suggests, this instrument has five holes on its conical point, which takein air during flight. The probe is actually a set of sensors that collectsaerodynamic data, including total air pressure, static air pressure, angle ofattack, and other measures that verify how well the vehicle is beingcontrolled—one of the primary objectives of the test.Because of the importance of this sensor, the five-hole probe is keptunder a protective cover, which will be removed by someone standing on top ofthe launch gantry and pulling it off with a lanyard. The cover will be removedabout 45 to 50 minutes before launch time. Once the cover is off, the five-holeprobe will be ready to slice through the air and make its contribution to theflight test…pointy end up, of course.

I was in the Field Artillery, and in our gun positions we had what was basically an intercom system between the guns and the fire direction center. At least once on each training exercise some anonymous joker would get on the horn and say “remember, pointy end goes in the tube first”.

The Ares I-X and Ares I designs are native to the U.S. While all rockets tend to look much alike, Ares I is unique in that much of the upper half (the “hammer head”) is wider then the lower half. A primary objective of the Ares I-X flight test is to determine how challenging it is to control a vehicle with this configuration.

Eddy – I can’t speak for the rest of the rocket, but the probe in the above photos was designed and assembled by the tiny company I work for (subcontracted by LMCO) in Blacksburg, Virginia. It’s 100% homegrown (and I suspect the more important parts of the rocket are too).

Back in the day the catch phrase was BEF. This means blunt end forward. In other words when you re-enter make sure the heatshield, or blunt end, comes in first. Otherwise it could ruin your entire day.